Smartwatches have spent years promising to track blood pressure without a cuff, and most have quietly needed one anyway. Google Research now says it has found a way around that requirement, using an AI model that looks for signs of hypertension in data from a standard smartwatch’s existing sensors, with no cuff calibration at all.
The approach is different from what most people would expect. The system doesn’t produce systolic or diastolic readings. Instead, it analyses several days of data from the watch’s optical pulse sensor and its accelerometer, which can detect both movement and the tiny wrist vibrations created by each heartbeat. Combined with the wearer’s height, the model outputs a probability that the person has persistently high blood pressure. The work, led by researchers Paolo Di Achille and Ming-Zher Poh, has been published in Nature.
That distinction matters. Current cuffless options, such as Samsung’s Galaxy Watch blood pressure feature, still require periodic calibration against a traditional cuff and essentially track changes from that baseline. Google’s model was instead trained without medical labels on more than 492,000 hours of sensor data from 2,109 people.
The clinical results are encouraging but far from conclusive. In a study of 196 participants across five US sites, measured against 24-hour ambulatory monitoring, the watch identified 65.8% of hypertension cases, compared with 55.3% for a single reading taken in a doctor’s office. It correctly ruled out the condition in 90% of people who didn’t have it. In a smaller follow-up group of 48 people whose first office reading was high, the watch outperformed repeat office visits, though several days of home cuff monitoring still caught more cases.
The limitations are significant. As a first screen, the watch still missed roughly a third of people with hypertension. Every participant was based in the US, had no known heart disease and was not taking blood pressure medication, so the results may not translate cleanly to a broader population. Google hasn’t said which watches can run the model or whether it has regulatory clearance.
Google does say the research helped shape the blood pressure trends feature in its Google Health app, and it is framing the work as a prompt to get checked rather than a diagnosis. That puts it in direct competition with Apple, whose Apple Watch hypertension notifications are already available in markets including the UAE and Saudi Arabia.
With Google estimating that more than half of the world’s billion-plus people with hypertension don’t know they have it, even an imperfect early warning has value. The harder question is whether users will treat a missed alert as a clean bill of health.